qga: Remove trivial "Returns:" sections

The QAPI doc generator recently started to auto-generate return
documentation when there is no "Returns:" section (commit 636c96cd77
"qapi: Fix undocumented return values by generating something").
Remove "Returns:" sections where the auto-generated text is obviously
no worse.  For instance, guest-info's documentation changes from

    Return:
       GuestAgentInfo -- GuestAgentInfo

to

    Return:
       GuestAgentInfo

The auto-generated returns all are in the exact same spot.

We did this for qapi/ in commit 0462da9d6b (qapi: remove trivial
"Returns:" sections).

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Daniel P. Berrangé <berrange@redhat.com>
Message-ID: <20250717115246.3830007-3-armbru@redhat.com>
Reviewed-by: John Snow <jsnow@redhat.com>

qga/qapi-schema.json

@@ -202,8 +202,6 @@
 #
 # Get some information about the guest agent.
 #
-# Returns: @GuestAgentInfo
-#
 # Since: 0.15.0
 ##
 { 'command': 'guest-info',
@@ -285,8 +283,6 @@
 # @count: maximum number of bytes to read (default is 4KB, maximum is
 #     48MB)
 #
-# Returns: @GuestFileRead
-#
 # Since: 0.15.0
 ##
 { 'command': 'guest-file-read',
@@ -320,8 +316,6 @@
 # @count: bytes to write (actual bytes, after base64-decode), default
 #     is all content in buf-b64 buffer after base64 decoding
 #
-# Returns: @GuestFileWrite
-#
 # Since: 0.15.0
 ##
 { 'command': 'guest-file-write',
@@ -387,8 +381,6 @@
 #
 # @whence: Symbolic or numeric code for interpreting offset
 #
-# Returns: @GuestFileSeek
-#
 # Since: 0.15.0
 ##
 { 'command': 'guest-file-seek',
@@ -428,9 +420,6 @@
 #
 # Get guest fsfreeze state.
 #
-# Returns: GuestFsfreezeStatus ("thawed", "frozen", etc., as defined
-#     below)
-#
 # .. note:: This may fail to properly report the current state as a
 #    result of some other guest processes having issued an fs
 #    freeze/thaw.
@@ -749,8 +738,6 @@
 #
 # Get list of guest IP addresses, MAC addresses and netmasks.
 #
-# Returns: List of GuestNetworkInterface
-#
 # Since: 1.1
 ##
 { 'command': 'guest-network-get-interfaces',
@@ -1251,8 +1238,6 @@
 #
 # Get information relating to guest memory blocks.
 #
-# Returns: @GuestMemoryBlockInfo
-#
 # Since: 2.3
 ##
 { 'command': 'guest-get-memory-block-info',
@@ -1298,8 +1283,6 @@
 #
 # @pid: pid returned from guest-exec
 #
-# Returns: GuestExecStatus
-#
 # Since: 2.5
 ##
 { 'command': 'guest-exec-status',
@@ -1458,8 +1441,6 @@
 #
 # Retrieves the timezone information from the guest.
 #
-# Returns: A GuestTimezone dictionary.
-#
 # Since: 2.10
 ##
 { 'command': 'guest-get-timezone',
@@ -1533,8 +1514,6 @@
 #
 # Retrieve guest operating system information
 #
-# Returns: @GuestOSInfo
-#
 # Since: 2.10
 ##
 { 'command': 'guest-get-osinfo',
@@ -1604,8 +1583,6 @@
 #
 # Retrieve information about device drivers in Windows guest
 #
-# Returns: @GuestDeviceInfo
-#
 # Since: 5.2
 ##
 { 'command': 'guest-get-devices',
@@ -1633,8 +1610,6 @@
 #
 # @username: the user account to add the authorized keys
 #
-# Returns: @GuestAuthorizedKeys
-#
 # Since: 5.2
 ##
 { 'command': 'guest-ssh-get-authorized-keys',